1. Field of the Invention
This invention relates to a device for coupling/fastening a pair of square bars made of metal or some other material and arranged squarely in abutment relative to each other at a squarely abutting corner of the bars.
2. Related Background Art
FIGS. 4 and 5 of the accompanying drawings schematically illustrate a known coupling/fastening device of the type under consideration. Referring to FIGS. 4 and 5, a longitudinal first engagement/anti-release groove c is formed in a first lateral surface b of the first square bar a and a second end facet e of the second square bar is made to squarely abut the first lateral surface b. A second engagement/anti-release groove g is formed in a second lateral surface f of the second square bar d.
To couple the first and second square bars a, d that are arranged squarely relative to each other, an L-shaped coupling metal fitting h, first and second bolts i, j and first and second nuts k, m are brought in and the rectangularly extending first and second wings h1, h2 of the coupling metal fitting h are made to respectively abut the first and second lateral surfaces b, f at the corner R defined by the first and second lateral surfaces b, f of the first and second square bars a, d.
Then, as shown in FIG. 5, the first and second bolts i, j are respectively put into first and second bolt receiving holes n, p bored respectively through the first and second wings h1, h2 and then driven into the first and second nuts k, m that have been put respectively into the first and second engagement/anti-release grooves c, g from the front ends thereof for mutual engagement. As the first and second bolts i, j are sufficiently tightened, first and second pairs of anti-release flanges q, r of the first and second engagement/anti-release grooves c, g formed respectively in the first and second lateral surfaces b, f of the first and second square bars a, d, each pair of anti-release flanges facing each other, are pinched respectively by the first and second bolts i, j and the first and second nuts k, m so that consequently the first and second square bars a, d are firmly coupled to and held rectangularly relative to each other.
Thus, while the above described known coupling/fastening device operates properly for coupling squarely arranged square bars, the first and second square bars may not be coupled and fastened to each other satisfactorily simply by tightly securing the L-shaped coupling metal fitting h to the first and second square bars by means of the first and second bolts. Additionally, the operation of aligning the first and second nuts k, m loosely put into the first and second engagement/anti-release groove c, g and the corresponding first and second bolts is practically a considerably cumbersome one that consumes considerable time and effort.
In view of the above identified drawbacks of known coupling devices, it is therefore an object of the present invention to provide a coupling device that comprises not an L-shaped coupling metal fitting h, first and second bolts i, j and first and second nuts k, m but an inner joint having first and second engagement sections to be sequentially and loosely put into first and second anti-release grooves formed in first and second square bars at a corner defined by corresponding lateral surfaces thereof and an outer joint to be engaged with the inner joint, said outer joint having a pair of lateral plates with a right-angled triangular profile and a rear plate section. Then, as a bolt is driven through the rear plate section into a threaded hole formed in the inner joint, the inner joint is slidably pressed against the flanges of the first and second engagement/anti-release grooves of the first and second square bars while the first and second abutting edges of the outer joint are slidably pressed against the first and second square bars so as to improve the coupling strength with which the first and second square bars are coupled to each other and raise the overall mechanical strength of the coupling members of the coupling device.
The above object of the present invention can be achieved more reliably when the profiles of the first and second engagement/anti-release grooves of the first and second square bars and those of the first and second engagement sections of the inner joint to be loosely put into the first and second engagement/anti-release grooves.
According to the invention, the above object is achieved by providing a device for coupling/fastening a pair of square bars including a first square bar having a first longitudinal engagement/anti-release groove formed in a first lateral surface thereof and a second square bar arranged to squarely abut the first square bar at an end facet thereof and having a second longitudinal engagement/anti-release groove formed in a second lateral surface thereof, said device comprising:
an inner joint having first and second engagement sections arranged rectangularly relative to each other and adapted to be loosely put into the first and second engagement/anti-release grooves of said first and second square bars respectively at a corner defined by said first and second lateral surfaces of said first and second square bars and a threaded hole bored through the central part thereof connecting said first and second engagement sections;
an outer joint having a rear plate section having a through hole bored at the center thereof and a pair of right-angled triangular lateral walls extending rectangularly from said rear plate section and adapted to be engaged with said inner joint so as to make the first and second abutting edges of said first and second lateral plates linked to each other by way of said rear plate section to be arranged at said corner of said first and second square bars;
a fastening bolt adapted to be driven into said threaded hole of said inner joint by way of the through hole bored through said rear plate section of said outer joint toward said corner so as to bring said inner joint closer to the rear plate section of said outer joint and force said first and second engagement sections of said inner joint loosely put into the first and second engagement/anti-release grooves of said first and second square bars respectively to slide and move, while pushing said first and second abutting edges of said outer joint against said first and second lateral surfaces of said first and second square bars respectively at said corner.
Preferably, the first and second engagement/anti-release grooves formed respectively in the first and second lateral walls of the first and second square bars show a T-shaped cross section and each of them includes a narrow front aperture defined by a pair of flanges projecting toward each other and having respective anti-release surfaces at the rear sides thereof and a wide rear groove section exposed to said anti-release surfaces, whereas the first and second engagement sections arranged rectangularly relative to each other of said inner joint show a corresponding T-shaped cross section and include respectively first and second pairs of grooves to be engaged with the corresponding flanges defining said narrow front apertures of said first and second engagement/anti-release grooves and first and second head sections to be loosely received in the respective wide rear grooves of said first and second engagement/anti-release grooves;
the pairs of abutting edges of said first and second head sections exposed respectively to said first and second pairs of grooves of said inner joint being forced respectively to slide on and be pressed against said anti-release surfaces of said pairs of flanges of said first and second engagement/anti-release grooves of said first and second square bars by driving said bolt into the threaded hole of the inner joint.